The use of widely varying copolyesters (CoPES) as adhesives has already been described many times in the literature in this field. Among these, it has been proposed to mix the copolyesters with softeners, especially for paste point coating, and indeed the use of softeners in the paste has been considered almost obligatory. Usually aromatic sulfonamide or oligomedc phthalic acid ester is used as the softener, which has the effect of lowering of the melting point and reducing the melting viscosity. Both phenomena lead to a reduction of the response temperature of the hot-melt adhesive, i.e. the glue can be used at lower temperatures.
The use of a softener, however, has a number of disadvantages. First, it increases the cost of the adhesive composition or paste. But a paste with a reduced proportion of softeners is preferable not only for economic reasons, but also for ecological reasons. The poor degradability or partial bactericidal action of sulfonamides in waste water should be mentioned in this connection, as well as the emission of partially volatile substances in the workplace.
It has also been proposed to use low melting point copolyesters. U.S. Pat. No. 4,551,521, for example, describes substances with a melting point between 60.degree. and 130.degree. C. But these compounds involve at least 70.5 mol % adipic acid and 70-99 mol % 1,4-cyclohexanedimethanol. Copolyesters (CoPES) with adipic acid, though, have the disadvantage that, through temperature and/or oxygen reactions, they produce strongly colored decomposition products, the formation of which can be prevented only by adding suitable stabilizers and antioxidants.
Outside the field of copolyester hot-melt adhesives, especially those useful at lower temperatures, a number of copolyetherester compositions have been proposed. Thus, EPA-O 204528 describes an adhesive film of a copolyetherester with at least 85 mol % (TPA), 65-97 mol % butanediol (BDO), and 3-35 mol % of a polyethylene glycol with a molar mass between 106 and 550 g/mol; triethylene glycol (TEDO) falls under this collective description. In these products for film formation, the melting point (determined by means of DSC), must be between 160.degree. and 200.degree. C. Hot-melt adhesives with such high melting points are useless for use in the textile field. Japanese patent disclosures JP 57/133217 and JP 57/095311 both describe the manufacture of fibers based on copolyetherester with up to 20% TEDO along with diol and hexamethylenediol or aliphatic dicarboxylic acids. Swiss patent disclosure CH-A-533 165 likewise concerns copolyesters of aromatic dicarboxylic acids and several glycols; the melting point of the described products is between 160.degree. C. and 220.degree. C., which is too high for use in the textile use region. German patent disclosure DE-A-32 39 413 describes molding compositions based on polybutylene terephthalate with 5-25 mol % of a linear alkanediol with 6-20 C atoms. European patent disclosure EP-A-120 618 describes thermoplastic copolyesters for glue sticks, consisting of 44-53 mol % TPA, 33-48 mol % IPA, and further aliphatic dicarboxylic acids with 4-12 C atoms, which contain at least 90 mol % butanediol as the diol component. Finally, Japanese patent disclosure JP 58/134114 describes copolyesters as hot-melt adhesives that consist exclusively of aromatic diacids (TPA/IPA=40-70/60-30 mol %) and up to 85-98 mol % butanediol, among other glycol components.
None of the aforementioned patent disclosures touch the present invention, which relates in particular to thermoplastic copolyester hot-melt adhesives with low melting points and very high crystallization rates, which can be used as textile hot-melt adhesives at low temperatures of application, and which show excellent resistance to dry cleaning and washing.